Diversity of endophytic bacteria from the cuprophytes Haumaniastrum katangense and Crepidorhopalon tenuis

Haumaniastrum katangense and Crepidorhopalon tenuis are two cuprophytes characteristic of the Katangan Copper Belt flora. We have studied the endophytic bacteria of H. katangense and C. tenuis as a first step to evaluate their potential contribution to plant adaptation to copper excess. Although their number varied considerably from sample to sample, culturable bacteria were found in roots and shoots of most plants. More than 800 isolates were screened for each plant species. Identification of isolates based on the sequence of the 16S rRNA gene, allocated them to 31 taxonomic units, belonging to 17 genera, mainly Proteobacteria. A great proportion of the bacteria were cupro-resistant and often resistant to other metals, especially zinc and cobalt, as well as nickel for the Methylobacterium isolates. Direct PCR amplification of the polymorphic bacterial internal transcribed spacer (ITS) from the plants’ organs DNA revealed a more diverse endophytic community, with more Gram+, among which a Rubrobacteridae that was never found associated with plants before. This work represents the first study of endophytes in Katangan cuprophytes